Acoustical building materials are widely used to control noise levels and reverberation in many different types of environments. Materials having a porous face are most commonly used to provide sound absorption. Sound enters through the face of the porous material and, as air moves back and forth within the material, the sound energy is converted into heat by friction. Conventionally, such acoustical material has been produced by wet-laying processes using slurries of suspended materials. The resulting products, however, have suffered from a variety of drawbacks. Specifically, because they are wet-laid, the fibers are closely packed so that sound cannot readily penetrate the board; thus, a wet-laid board must be perforated or fissured in order to obtain acceptable acoustical performance. In addition, excessive energy usage results from the drying of wet-laid board products. For these reasons, much recent interest has related to acoustical boards which are produced by dry-forming procedures.